The 1-2-3 superconductor has a structure similar to perovskite. The resulting unit cell consists of.

The 1-2-3 superconductor has a structure similar to perovskite. The resulting unit cell consists of three stacked cubic unit cells; it is considered to be orthorhombic rather than cubic, having an almost square base, but rectangular sides (a = 3.817_ b = 3.882_ c = 11.671_. Figure 5. The idealized structure of YBa2Cu3O7 shows evolution from the perovskite structure of Figure 4. (a) Stacking of 3 perovskite units; (b) Shift of the origin; (c) Removal of some of the oxygens to the give correct chemical composition. Questions: 1. The copper in YBa2Cu3O7 may be considered to be a mixture of +2

question The 1-2-3 superconductor has a structure similar to perovskite. The resulting unit cell consists of three stacked cubic unit cells; it is considered to be orthorhombic rather than cubic, having an almost square base, but rectangular sides (a = 3.817_ b = 3.882_ c = 11.671_. Figure 5. The idealized structure of YBa2Cu3O7 shows evolution from the perovskite structure of Figure 4. (a) Stacking of 3 perovskite units; (b) Shift of the origin; (c) Removal of some of the oxygens to the give correct chemical composition. Questions: 1. The copper in YBa2Cu3O7 may be considered to be a mixture of +2 and +3 oxidation states. If Y has a +3 oxidation state and Ba and O have their normal oxidation states, what fraction of the copper is in each of the two oxidation states? 2. In your laboratory notebook, draw the idealized tetragonal unit cell if the yttrium and barium cubic structures were based exactly on the perovskite sub-structure. 3. Compare the coordination numbers of barium and yttrium in both the ideal perovskite sub-structure and the actual structure. 4. Comparing the two structures, speculate as to why the 1-2-3 oxide structure may exhibit superconductivity. 5. Show that the orthorhombic unit cell corresponds to the formula YBa2Cu3O7. Remember that an atom shown as part of a unit cell is shared equally between neighbouring unit cells, unless it is entriely enclosed within the unit cell.